A patch clamping method is known as a conventional method of screening candidate pharmaceuticals by monitoring electrical activity of a cell in order to select effective pharmaceutical. In the patch clamping method, a hollow glass tube having a microscopic tip is inserted directly into a cell, thereby measuring a difference between an inside and outside of the cell. (For instance, “Single Channel Currents Recorded From Membrane of Enervated Frog Muscle Fibers”, Nature 260: 799-802, Neher E & Sakmann B, 1976) This method provides accurate measurement of the status of activities of an ion channel existing in a cell membrane.
International Publication No. WO02/055653 discloses a device and a method for measuring an extracellular electric potential. This device includes a substrate having a holding section and electrodes to measure an extracellular electric potential. This device provides data as accurate as data provided by the patch clamping method, and measures a large amount of samples easily and quickly.
FIG. 24 is a sectional view of the above-mentioned device for measuring an extracellular electric potential. Culture solution 51 is put in container 50. Target cell 52 is caught and held with the holding section provided at substrate 53. This holding section is formed with cavity 54, opening 55, and through-hole 56 which are all formed in substrate 53, and hole 56 communicating with cavity 54. Reference electrode 58 is provided in container 50. Measuring electrode 57 is provided near through-hole 56. Electrode 57, a sensing section, is coupled to an external signal detector via wiring.
Target cell 52 is sucked via through-hole 56 by a suction pump from the outside, contacts cavity 54, thus being held at cavity 54. Electrical signals produced by activity of target cell 52 is detected as an electric potential difference between measuring electrode 57 disposed near through-hole 56 and reference electrode 58 without leakage into culture solution 51.
This conventional device includes substrate 53 having cavity 54 and through-hole 56 formed therein and container 50 provided on substrate 53. Container 50 is used for receiving and storing culture solution and chemicals. This structure, therefore, cannot measure electric potentials of cells floating in the solution in a large space as it is in this environmental condition.
The conventional device has two areas partitioned with substrate 53, namely, one area having target cell 52 therein and the other area having measuring electrode 57, and cannot introduce respective culture solutions or chemicals different from each other into the areas.